Despite his (alleged) nickname, “Middle-Class Joe” Biden doesn’t seem to understand the middle class. It’s become customary for Democratic presidential candidates to vow not to raise taxes on this particular group of voters. Hillary Clinton repeatedly made that pledge in 2015 and ’16—a tactic Barack Obama also used in 2008. It’s a commitment that sounds nice on the campaign trail, but it hamstrings policy-making. And now Biden, as the 2020 Democratic nominee, has made that bad promise even worse.

Bill and Hillary Clinton and Obama used the same cutoff for middle-class tax protection: those who earn $250,000 a year or less. It’s a preposterous definition of the middle class. But Biden has seen their $250,000 bid and nearly doubled it.

“Nobody making under 400,000 bucks would have their taxes raised, period, bingo,” he told CNBC in May, repeating the promise in August on ABC. His campaign is so dedicated to this pledge that his economic advisers gave Glenn Kessler of The Washington Post detailed workarounds that would result in, they say, no new taxes for anyone earning $400,000 or less.

Certainly the middle class has always been an amorphous idea. But it should at least nominally refer to the middle of the country’s income distribution. And $400,000 ain’t it. According to the most recent census data, median annual household income in the United States is $68,703. Even with an expansive view of how much income on either side of that mark could still qualify as middle class, it’s impossible to see how a figure nearly six times the median would count. Rather, $400,000 a year lands a household easily in the richest 5 percent.

Allowing these families to think of themselves as middle class has perverse outcomes. That distorted view of reality makes it appear as if we’re doing a better job of distributing wealth than we are. It also causes the rich to feel deserving of government benefits that would be better targeted to poorer households. Take tax breaks, which mostly flow to the richest 20 percent of Americans: That’s money that could be spent to help low-­income households afford food, housing, and child care.

Letting them call themselves middle class also makes them bristle at the idea that they should chip in more to fund programs that benefit the rest of us. Obama knows this well. When he tried to levy taxes on college savings accounts, which overwhelmingly benefit families that make more than $200,000, and use the money to subsidize college for low- and middle-income people, the swift backlash that he was violating his campaign pledge led him to drop the plan just a week after he proposed it.

Making a clear promise not to raise taxes on people earning less than $400,000 will hamper Biden’s ability to enact smart policies in response to the country’s most pressing needs. Take paid family leave. Just 16 percent of private sector workers get paid family leave from their employers, leaving everyone else to cut back on spending or go into debt to take time off. Biden recognizes this problem and has promised to provide 12 weeks of paid family and medical leave a year.

This would fulfill a desire congressional Democrats have had since 2013, when they introduced the Family Act, which would levy small payroll taxes (structured like Social Security taxes) and put that money into a fund that would pay out when employees needed paid leave to care for themselves, a new baby, or a sick or disabled family member.

But it would raise taxes on everyone, so it would seem to be an option Biden has forsworn, even though it’s the model that the vast majority of other countries have chosen. Such a wrinkle led Hillary Clinton to craft a paid leave policy that would have raised its money entirely from taxing the wealthy, making paid family leave appear to be a handout to the less fortunate rather than something we all owe one another.

There are plenty of progressive policy goals that would be difficult to pull off without increasing taxes on more than just the richest few. Universal health care and universal child care are two that come to mind.

Even if the middle and lower classes saw their tax bills rise to fund such programs, they would almost certainly receive more in benefits. But we can’t start that conversation if the Democratic nominee for the White House won’t even contemplate tax increases below a certain threshold. To debate policies to make our country more equal, we must first be honest about our class divisions.